Field of the Invention
The present invention relates generally to a low voltage dimmer and more specifically it relates to a TRIAC low voltage dimming control system for effectively controlling the dimming of low voltage lighting using a TRIAC dimmer.
Description of the Related Art
Any discussion of the related art throughout the specification should in no way be considered as an admission that such related art is widely known or forms part of common general knowledge in the field.
Low voltage lighting has become increasingly popular in various applications such as but not limited to light-emitting diode (LED) based lighting, under cabinet lighting, TV back lighting, staircase lighting, architectural lighting, bar lighting, kitchen lighting, toe kick lighting, ceiling cove lighting, ceiling can lighting, troffer lighting, decorations, landscape lighting and vehicles. Most low voltage lighting utilizes low-voltage direct current (DC) electrical power that is less than 120V DC such as 12V DC, 24V DC or 48V DC.
LED based lighting has become an increasingly popular type of low voltage lighting because of the low power, low heat and color changing characteristics of LED lights. Examples of LED based lighting include LED light fixtures, LED light bulbs, LED light strips, flexible LED light strips, outdoor LED lighting, LED landscape lighting, recessed LED lighting, LED security lighting and LED flat panel lights. To illustrate one type of LED based lighting, a flexible LED light strip is comprised of an elongated flexible strip of printed circuit board (PCB) having two or more electrically conductive traces to provide electrical power, a plurality of light-emitting diodes attached along the front surface of the flexible strip and electrically connected to the conductive traces, and a length of adhesive along the back surface of the flexible strip.
Low voltage power supplies are used to convert high voltage alternating current (AC) electrical power (e.g. 120V AC, 240V AC) to low voltage direct current (DC) electrical power (e.g. 12V DC, 24V DC, 48V DC) to provide low voltage DC electrical power to various electrical devices such as low voltage lighting including LED lighting. Low voltage power supplies are often times referred to as “AC/DC power supplies”, “switch-mode power supplies” or “magnetic low-voltage transformers”. Low voltage power supplies are typically comprised of a magnetic transformer electrically connected in series with a rectifier to create a single-phase rectifier circuit that converts 120V AC to a low voltage (e.g. 12V DC). U.S. Pat. No. 3,353,083 (Greenberg) discloses an exemplary AC/DC power supply using a magnetic transformer and rectifier in series to convert AC electrical power to DC electrical power. Low voltage power supplies are used to provide electrical power to various types of low voltage lighting.
There are two main types of low voltage dimmers used to control light emitted from LED based lighting: Pulse-width modulation (PWM) LED dimmers and analog LED dimmers. PWM LED dimmers control the duty cycle of the low voltage power supplied to the LED based lighting thereby adjusting the luminosity of the LED lights. Analog LED dimmers provide variable current to the LED based lighting either through limiting the current or adjusting the applied voltage thereby changing the luminosity of the LED lights.
Conventional AC based light dimmers such as TRIAC (triode for alternating current) dimmers (a.k.a. TRIAC dimmer switches) are commonly utilized to dim AC high voltage lighting (e.g. incandescent or halogen lighting) which typically operate at 120V AC. TRIAC dimmers typically have a sliding dimmer switch (a.k.a. “slide dimmer”), rotating knob switch (a.k.a. “rotary dimmer”) or a plurality of buttons to select a desired dimming level for lights. TRIAC dimmers may also have a power switch to allow for turning off or on the electrical power from the TRIAC dimmer regardless of the position of the dimmer control switch. TRIAC dimmers are widely available in stores and come in various colors, designs and configurations thereby allowing consumers to select from a wide variety of dimmer switch options.
Because a conventional TRIAC dimmer is designed to be only used with a pure resistive load (e.g. incandescent light bulb or halogen bulb), TRIAC dimmers are not suitable for use in combination with low voltage power supplies which are an inductive load. Hence, manufacturers and end users have been forced to utilize dimmers that are specifically designed for low voltage lighting.
Because of the inherent problems with the related art, there is a need for a new and improved TRIAC low voltage dimming control system for effectively controlling the dimming of low voltage lighting using a TRIAC dimmer.